Rain showers & rain developing. Winds shifting NE-N and increasing to 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges and plateaus by morning. Cloud bases dropping with dense fog formation on higher ridges. Temps dropping into the 50s to around 60 degrees by morning ( 40s wind chills at highest elevations ).
Saturday Morning-Afternoon
A chance of rain showers-drizzle. Windy & chilly. Low cloud bases with dense fog above 2500-3000 feet along and north of the High Knob Massif & Tennessee Valley Divide. Becoming partly cloudy late. Winds N to NE at 10-20 mph, with higher gusts. Temps steady or falling into 50s lower-middle elevations and dropping to the 40s-low 50s in upper elevations. Wind chills in upper 30s to lower 40s at highest elevations. Milder conditions lee of the High Knob Massif into river valleys of the Clinch, Powell & Holston drainages.
Saturday Night Into Sunday Morning
Becoming clear. Chilly. Windy across mid-upper elevation mountain ridges. Winds N-NE 5-15 mph, with higher gusts, along middle elevation ridges-plateaus below 2700 feet. N-NE winds 10-20 mph, with higher gusts, on upper elevation mountain ridges. Temperatures dropping into the 30s to lower 40s ( frost and/or fog could occur in any valleys that might be able to decouple, with light-calm winds ). Wind chills in 30s and 40s along ridges-plateaus, except locally into the 20s to lower 30s during gusts on high peaks.
Sunday Afternoon
Sunny. Seasonably cool. N winds 5-15 mph, with higher gusts. Temperatures varying from mid-upper 40s in the upper elevations to the mid 50s to around 60 degrees ( wind chills continuing to be a factor at highest elevations ).
Sunday Night Into Monday Morning
Clear. Frost possible in colder valleys. Winds NNW-NNE at 5 to 15 mph, with some higher gusts, along the mid to upper elevation mountain ridges. Temperatures varying from the upper 20s to lower 30s in colder valleys to the upper 30s to lower 40s ( fog possible along main streams-lakes ).
*Multiple nights with the potential of frost formation in mountain valleys is being watched for into the new work week.
Weather Discussion ( Big Changes )
Saturday Night Update
My update Saturday Night is to decrease sustained wind speeds a little into Sunday AM, following a very windy Saturday afternoon in mid-upper elevations.
Orographic forcing aided rainfall amounts as the pressure gradient increased Saturday across the High Knob Massif area, with 1.00″ to 1.50″ rain amounts being common.
This included the water plant at Appalachia Lake where Mark Quillin reported 1.38″ of rainfall. This was in contrast to only 0.31″ of rain measured in Clintwood and just 0.25″ measured lee of the mountains in the Tri-Cities.
High Knob Massif MesoNET
An average MIN of 42.1 degrees was observed in the wetland valley during the past 10 days ( i.e., September 28-October 7 period ).
Most of the massif area was engulfed in clouds, with high valleys holding steady near 60 degrees until early Saturday afternoon when a temperature drop started ( temps were several degrees cooler atop adjacent ridges all day ).
By late Saturday afternoon wind chills were notable along the high ridges, as my Field Studies In Microclimatology Class can testify too ( despite layered clothing it felt cold as strong winds swirled fog & occasional rain showers across the high country ).
Many leaves came down, and partially covered roads in the massif, as color is really increasing from Wise on upward in elevation. Hopefully, below the highest ridges, this leaf fall will not be detrimental to the upcoming peak.
Previous Discussion
ALERT For Dense Fog Developing Into Saturday Morning At Middle-Upper Elevations Along And North Of The High Knob Massif & Tennessee Valley Divide
High Knob Massif Webcam – University Of Virginia’s College At Wise
Orographic pilatus clouds capping the High Knob Massif late Friday was a signal of big weather changes into this weekend, as the pressure gradient around Matthew cranks up orographics behind a passing cold front pushing across the Appalachians. This means a CHILLY weekend ahead!
NAM 4 KM Model 10 M Wind & Streamline Forecast at 6 AM Saturday
As Hurricane Matthew crawls along the South Carolina coast an increasing northerly flow will develop across the Appalachians, increasing upslope into the High Knob Massif and Tennessee Valley Divide during the predawn-morning hours of Saturday. This will cause a drop in cloud bases, with dense fog formation engulfing higher terrain locales above the 2500-3000 foot level ( e.g., amid, or just above, the Town of Wise & Sandy Ridge on upward in elevation ).
NAM 4 KM Model 10 M Wind & Streamline Forecast at 2 PM Saturday
Drier air will eventually get pulled into the circulation, but low clouds ( and dense fog at higher elevations ) could last for much of the day Saturday before dissipating ( with a rise in cloud bases likely before a complete clearing by Saturday Night into Sunday morning when some valleys could then develop fog as others develop frost IF vertical mixing can locally relax enough to allow a run at dewpoints, which remains to be seen as Matthew churns ).
Most all of this weekend will be dominated by gusty winds across higher elevations, especially mountain ridges, where frost will not be able to form but true wind chills will be felt for the first time ( for a prolonged period ) this autumn.
As the pressure gradient begins to relax, Sunday Night into Monday AM will offer a much better chance for formation of frost in colder mountain valleys. Stay tuned.
